1. Field of the Invention
The present invention relates to a cellular phone, and more particularly, to a foldable cellular phone having a main body, a key pad disposed on the main body, a folder folding and rotating with respect to the main body, and a LCD display, and a method thereof.
2. Description of the Related Art
Generally, a cellular (wireless or mobile) phone is classified into one of a bar type having a key pad exposed outside, a flip type having the key pad covered by a cover, and a folder type folding in half.
The folder type cellular phone includes a main body having a key pad, and a folder having an LCD display and being folded with respect to the main body. The key pad of the main body is exposed to an outside of the cellular phone. According to a folding operation of the folder according to Japanese patent publication (patent publication no. 11-30226), the folder is not only foldable with respect to the main body but also rotatable with respect to the main body in an open (unfolded) state to meet various user demands.
FIG. 1 is a perspective view showing the cellular phone of the Japanese patent publication. The cellular phone includes a main body 4 having a key pad 3, and a folder 2 folded and unfolded with respect to the main body 4 and having an LCD display 1.
The main body 4 includes one end provided with a pair of cylindrical supports 5 and a cylindrical hinge 5a rotatably fixed between the cylindrical supports 5, and the folder 2 is rotatably connected to a lower portion of the cylindrical hinge 5a to be folded and unfolded in a direction of an arrow A.
The folder 2 is provided with a rotation unit 10 rotating the folder in a direction of an arrow B. The rotation unit 10 is vertically and/or fixedly coupled to the cylindrical hinge 5a to rotate with respect to the cylindrical hinge 5a and is coupled to the folder 2.
FIG. 2 is a cross-sectional view showing the rotation unit 10 provided on a lower portion of the folder 2 of the cellular phone shown in FIG. 1. As shown in FIG. 2, the rotation unit 10 includes a rotation shaft 6 having a hollow cylindrical structure coupled to the lower portion of the folder 2, a fixed shaft 7 fixed on the cylindrical hinge 5a to correspond to the rotation shaft 6, a nut coupled of the fixed shaft 7, and a coil spring 9 extended (released) and compressed by the nut 8.
The rotation shaft 6 includes an inward flange 6a having a portion formed on a lower portion of the rotation shaft to be bent in an inward direction of a hollow inside of the rotation shaft 6, a boss 7a formed on the fixed shaft 7 in a lengthwise direction along a center line of the fixed shaft 7 to protrude toward the inward direction, and a screw formed on an outer surface of the boss 7a. 
The boss 7a of the fixed shaft 7 is inserted into the inward flange 6a through the hollow inside of the rotation shaft 6, and the coil spring 9 and the nut 8 are sequentially disposed on the outer surface of the boss 7a of the fixed shaft 7.
The nut 8 is coupled to the screw of the boss 7a, the coil spring 9 is disposed between the nut 8 and the inward flange 6a so that the coil spring 9 is not released from an outside of the boss 7a of the fixed shaft 7 due to the nit 8 and the inward flange 6a. 
When a user rotates the folder 2 with respect to the main body 1 in the direction of the arrow B according to a user manipulation, the rotation shaft 6 rotates in the same direction B as the folder 2 while being supported by the coil spring 9, so that the folder 2 rotates with respect to the center line of the rotation unit 10.
In the cellular phone having the above structure, since the cylindrical hinge 5a is rotatably supported by the cylindrical support 5 of the main body 4 to enable the folder 2 to rotate the folder 2 with respect to the main body 4. When the folder 4 is opened with respect to the main body 4, the folder 2 is rotated with respect to the center line of the fixed unit 10 so that the user is able to see the LCD display 1 in a desirable direction.
Since the folder 2 is rotates in the direction B according to the user manipulation of the cellular phone at a user hand, it is very inconvenient that the user should hold at according to the user manipulation of the cellular phone while the user needs to rotate the folder 2 using the other hand.
The user needs to use both hand to rotate the folder as described above. If the user holds the cellular phone using the both hand, the user cannot rotate the folder 2 with respect to the main body 2 in the direction B.
If a camera (not shown) is mounted on the main body 4, an image sensed through the camera can be displayed on the LCD display 1 to show a state of the sensed image.
However, when the user needs to show the sensed image in an opposite direction, the folder 2 having the LCD display 1 needs to display the image in an opposite direction of a front surface of the camera. Therefore, the user needs to manually open the main body 4.